I'm sure that we expats celebrated memorial day weekend when we were in the US in one way or the other. The thing is that there are not that many Americans in Cabarete, and since it is not a holiday here but just one more work day, especially for those of us who work weekends.... You won't see celebrations for the 4th of July either (I miss them!!), but our family still celebrates Thanksgiving.
Anyway, if there's enough of you coming on Memorial Day weekend I'll be glad to organize a get together (that's if I'm back; in Virginia for a few more weeks).